A communication system can be seen as a facility that enables group communication between two or more entities such as user terminal and/or other nodes associated with the communication system. Subscribers, such as the users or end-users, to a communication system may be offered and provided numerous services, such as calls, data communication or multimedia services or simply an access to a network, such as the Internet. The services may be offered by an operator of the communication system or by an external service provider.
A communication system typically operates in accordance with a given standard or specification setting out what the various entities associated with the communication system are permitted to do and how that should be achieved. A standard or specification may define a specific set of rules, such as communication protocols and/or parameters, on which connections between the entities can be based.
Examples of communication systems may include fixed line communication systems, such as a public switched telephone network (PSTN), wireless communication systems, e.g. global system for mobile communications (GSM), general packet radio service (GPRS), universal mobile telecommunications system (UMTS), wireless local area network (WLAN) and so on, and/or other communication networks, such as an Internet Protocol (IP) network and/or other packet switched data networks. Various communication systems may simultaneously be concerned in a connection. An end-user may access a communication network by means of any appropriate communication device, such as user equipment (UE), a mobile station (MS), a cellular phone, a personal digital assistant (PDA), a personal computer (PC), or any other equipment operable according to a suitable network protocol, such as a Session Initiation Protocol (SIP) or a wireless applications protocol (WAP) or a hypertext transfer protocol (HTTP). The user equipment may support, in addition to call and network access functions, other services, such as short message service (SMS), multimedia message service (MMS), electronic mail (email), Web service interface (WSI) messaging and voice mail.
Services offered to subscribers of a communication system may comprise conferencing services, such as multiparty conferencing, for example so-called direct voice communication services. The direct voice communication service may allow users to engage in immediate communication with one or more users. One example of the direct voice communication services may comprise the “push-to-talk over cellular” (PoC) service also known as the PTT (push-to-talk service). The PoC may be based on Voice over IP (VOIP) technology in cellular networks, such as the GSM/GPRS network.
Services offered to subscribers of a communication system may comprise instant messaging. The instant messaging communication service may allow users to send messages with one or more users. The instant messaging refers to the transfer of messages between users in near real-time. These messages are usually, but not required to be, short. Instant messages are often used in a conversational mode, that is, the transfer of messages back and forth is fast enough for participants to maintain an interactive conversation. A sent message may be just a plain text or it may contain some payload such as picture or application.
The direct voice communication services may use capabilities of, for example, the Internet Protocol Multimedia Subsystem (IMS), which is an example of a system providing multimedia services. The IMS enables IP connections for a communication device and other parties to the communication, such as other communication devices or entities associated with the network. The third generation partnership project (3GPP) has defined use of the GPRS for offering IP connectivity to IMS services.
Patent Application US 2002/0150091, filed on 17 Apr. 2001, in the name of Lopponen et al., discusses about a packet mode, e.g. IP, group communication service layer provided on top of a standard mainstream cellular network.
US Patent Application, filed on 23 Aug. 2004, claiming priority from FI 20040577 (23 Apr. 2004), in the name of Poikselkä et al., discusses about providing information on a resource in a communication system, such as whether the resource comprises an individual user identity or a plurality of user identities.
Open Mobile Alliance (OMA) OMA-RD_PoC-V1—0-20040628-C, Push to Talk over Cellular Requirements, version 1.0-28 Jun. 2004, defines the PoC, which is based on half-duplex communications. Thus, one user subscribing the PoC service, i.e. a first PoC subscriber, and belonging to a group may speak at the time and the other users, or PoC subscribers, belonging to the group may listen, but may not talk at the same time. The first PoC subscriber may select a person or groups of persons to talk to, for example, from a directory or the like provided in a communication device the first PoC subscriber is using. The first PoC subscriber may press and hold a push-to-talk key on the communication device to start talking. The first PoC subscriber can now talk for as long as the first PoC subscriber holds the key. The push-to talk key may be a specific button, tangent or any other appropriate key in a user interface. Similar principles apply with devices having touch sensitive or sound activated user interfaces. Bi-directional communication may be offered since all parties of the communication session may similarly communicate voice data with the PoC application server, which is an example of an entity controlling the PoC session. As soon as the first PoC subscriber releases the push-to-talk key, another member of the group may reserve a turn to speak. A turn to speak may be requested by pressing the push-to-talk key. The PoC application server or another controlling entity may grant a turn to speak on a first come first served basis or based on priorities. Talk bursts in the PoC conferences are usually connected without the recipient answering and typically received through a built-in loud speaker of a communication device.
In a group communication, a party which is the target of a connection attempt, namely the called party or recipient, might need or want to receive identity of an initiating party, namely the calling user identity, and also a group identity (group ID) of the group into which the called party is intended to participate
For example, in the PoC system, a PoC client, such as software in a communication device, may use a group identity for learning or determining other members in the group and performing joining the group.
In addition to the group identity, a recipient client may need or want to learn details on the group. For example, in many group services, there are several types of groups that behave in different manners from a point of view of an end user. For example, the OMA-RD_PoC-V1—0-20040628-C, paragraph 6.1.2 defines following three group types: ad-hoc, pre-arranged and chat.
A group, such as an ad-hoc and chat group, may be temporary. The recipient client should not store a group ID of a temporary group, as the group ID may not be valid after the session to which the group ID relates is over. On the other hand, persistent groups also exist, pre-arranged PoC group being an example. A recipient client may store a group ID of a persistent group for later use, e.g. to initiate a new session.
It might be advantageous to a recipient client to learn the group type. For example, the recipient client might thus be able to decide whether the group ID should or need to be stored and how the group ID may be used.
So-called Industry Consortium Specifications [Push-To-Talk over Cellular (PoC); Signaling Flows—UE to Network Interface (UNI) and Push-To-Talk over Cellular (PoC) Signalling Flow—Network-to.Network interface (NNI); PoC Release 2.0] use a “From” to transport the calling party identity when the talk session is an instant personal talk or an ad-hoc instant group talk. When the talk session is an instant group talk or a chat group talk then a “From” header transports the group identity of the group. A “Referred-By” header is used to transport the calling party address in case of an instant group talk or to a chat group talk. The problem in this approach may be that a recipient cannot trust to information given in the “From” header, as a sending client or end user may be able to fill the “From” header freely without a Session Initiation Protocol (SIP) network, such as IMS, validating the “From” header. Also, use of the “Referred-by” header outside of the context of a REFER method may be against SIP principles.
It shall be appreciated that these issues are not limited to any particular communication environment, but may occur in any appropriate communication system.